From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B7CF3B52F0 for ; Thu, 2 Apr 2026 16:51:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775148682; cv=none; b=ip5KCGEh6F46rf/yW/FubUj4ZEBHvHTuhss8x5vPF9OeFL43BVmGGlDvwglCRRzs39QFZ1d+NbfvWQTu2sEyWq3QBeuUEdSJTi66SjPrkHjRz2FYaQMVsGHO6jY/kJJQA6ueoSyljwrIL9XFBoZuIgxelHpVomrIC5p56bGbwyg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775148682; c=relaxed/simple; bh=cfPHypPsTAyk5BrdXJH/XsdupzO755bHeMVkkuXim2g=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=USQOecvU+cLJcP2skOIcsidnpMOqD6kndkLS/RRDZCr+ncAvyftCYfGgr+Im+YV8nY7YZDkxMigKTnCZo7wKqvLx9mYCL2jrOr7XitGDsMN2AbCW7gZXXv+Sd2Tdta++0WLxmRf5vXcD89TJPNKi0tXI/hPTvDD7FB94f0nLb/k= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=fXIrMarD; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="fXIrMarD" Received: by smtp.kernel.org (Postfix) with ESMTPSA id B89B9C116C6; Thu, 2 Apr 2026 16:51:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1775148681; bh=cfPHypPsTAyk5BrdXJH/XsdupzO755bHeMVkkuXim2g=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=fXIrMarD5AkN5uDEE99AYJ2o9CZCDky7AwfErTzM45/DsNqTU8IQU7+sFoqaSdgVm zAB+WU8pk9anmreZ6lFzXypESpLsYJmol7weZhC3hsnzcG0Ej3SnZvvi6ghdzu9dFZ Zvgou1YXuU5tPqW4fXnK/u1Nhugmwe0kRVpdhwqTBE+3P8L9zANPgtR77w1iquHZ9W s5TJAqmBNi7J3KLmSoGP5nAUCDo6jQ4nMZQyN3RFq4zir4QkVPXeyG6xBbrCsDCSRy cDEWiSAepzFcWOYYDZA0967LkbzMx/QV75mymyC5tBb3aglipBhnMnUkJy4k6tY1+K Cqz5InQ4O7lPQ== From: Sasha Levin To: stable@vger.kernel.org Cc: Li Chen , Jan Kara , Theodore Ts'o , stable@kernel.org, Sasha Levin Subject: [PATCH 6.12.y] ext4: publish jinode after initialization Date: Thu, 2 Apr 2026 12:51:19 -0400 Message-ID: <20260402165119.1482773-1-sashal@kernel.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <2026033001-abstract-hangup-400d@gregkh> References: <2026033001-abstract-hangup-400d@gregkh> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Li Chen [ Upstream commit 1aec30021edd410b986c156f195f3d23959a9d11 ] ext4_inode_attach_jinode() publishes ei->jinode to concurrent users. It used to set ei->jinode before jbd2_journal_init_jbd_inode(), allowing a reader to observe a non-NULL jinode with i_vfs_inode still unset. The fast commit flush path can then pass this jinode to jbd2_wait_inode_data(), which dereferences i_vfs_inode->i_mapping and may crash. Below is the crash I observe: ``` BUG: unable to handle page fault for address: 000000010beb47f4 PGD 110e51067 P4D 110e51067 PUD 0 Oops: Oops: 0000 [#1] SMP NOPTI CPU: 1 UID: 0 PID: 4850 Comm: fc_fsync_bench_ Not tainted 6.18.0-00764-g795a690c06a5 #1 PREEMPT(voluntary) Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.17.0-2-2 04/01/2014 RIP: 0010:xas_find_marked+0x3d/0x2e0 Code: e0 03 48 83 f8 02 0f 84 f0 01 00 00 48 8b 47 08 48 89 c3 48 39 c6 0f 82 fd 01 00 00 48 85 c9 74 3d 48 83 f9 03 77 63 4c 8b 0f <49> 8b 71 08 48 c7 47 18 00 00 00 00 48 89 f1 83 e1 03 48 83 f9 02 RSP: 0018:ffffbbee806e7bf0 EFLAGS: 00010246 RAX: 000000000010beb4 RBX: 000000000010beb4 RCX: 0000000000000003 RDX: 0000000000000001 RSI: 0000002000300000 RDI: ffffbbee806e7c10 RBP: 0000000000000001 R08: 0000002000300000 R09: 000000010beb47ec R10: ffff9ea494590090 R11: 0000000000000000 R12: 0000002000300000 R13: ffffbbee806e7c90 R14: ffff9ea494513788 R15: ffffbbee806e7c88 FS: 00007fc2f9e3e6c0(0000) GS:ffff9ea6b1444000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000010beb47f4 CR3: 0000000119ac5000 CR4: 0000000000750ef0 PKRU: 55555554 Call Trace: filemap_get_folios_tag+0x87/0x2a0 __filemap_fdatawait_range+0x5f/0xd0 ? srso_alias_return_thunk+0x5/0xfbef5 ? __schedule+0x3e7/0x10c0 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ? srso_alias_return_thunk+0x5/0xfbef5 ? cap_safe_nice+0x37/0x70 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ? srso_alias_return_thunk+0x5/0xfbef5 filemap_fdatawait_range_keep_errors+0x12/0x40 ext4_fc_commit+0x697/0x8b0 ? ext4_file_write_iter+0x64b/0x950 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ? srso_alias_return_thunk+0x5/0xfbef5 ? vfs_write+0x356/0x480 ? srso_alias_return_thunk+0x5/0xfbef5 ? preempt_count_sub+0x5f/0x80 ext4_sync_file+0xf7/0x370 do_fsync+0x3b/0x80 ? syscall_trace_enter+0x108/0x1d0 __x64_sys_fdatasync+0x16/0x20 do_syscall_64+0x62/0x2c0 entry_SYSCALL_64_after_hwframe+0x76/0x7e ... ``` Fix this by initializing the jbd2_inode first. Use smp_wmb() and WRITE_ONCE() to publish ei->jinode after initialization. Readers use READ_ONCE() to fetch the pointer. Fixes: a361293f5fede ("jbd2: Fix oops in jbd2_journal_file_inode()") Cc: stable@vger.kernel.org Signed-off-by: Li Chen Reviewed-by: Jan Kara Link: https://patch.msgid.link/20260225082617.147957-1-me@linux.beauty Signed-off-by: Theodore Ts'o Cc: stable@kernel.org [ adapted READ_ONCE(ei->jinode) to use pos->jinode ] Signed-off-by: Sasha Levin --- fs/ext4/fast_commit.c | 4 ++-- fs/ext4/inode.c | 15 +++++++++++---- 2 files changed, 13 insertions(+), 6 deletions(-) diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index 6fb0cd4aeaefe..3ee282c8d2481 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -997,7 +997,7 @@ static int ext4_fc_submit_inode_data_all(journal_t *journal) finish_wait(&ei->i_fc_wait, &wait); } spin_unlock(&sbi->s_fc_lock); - ret = jbd2_submit_inode_data(journal, ei->jinode); + ret = jbd2_submit_inode_data(journal, READ_ONCE(ei->jinode)); if (ret) return ret; spin_lock(&sbi->s_fc_lock); @@ -1022,7 +1022,7 @@ static int ext4_fc_wait_inode_data_all(journal_t *journal) continue; spin_unlock(&sbi->s_fc_lock); - ret = jbd2_wait_inode_data(journal, pos->jinode); + ret = jbd2_wait_inode_data(journal, READ_ONCE(pos->jinode)); if (ret) return ret; spin_lock(&sbi->s_fc_lock); diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 6b679c638128d..a0b68b9d96266 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -128,6 +128,8 @@ void ext4_inode_csum_set(struct inode *inode, struct ext4_inode *raw, static inline int ext4_begin_ordered_truncate(struct inode *inode, loff_t new_size) { + struct jbd2_inode *jinode = READ_ONCE(EXT4_I(inode)->jinode); + trace_ext4_begin_ordered_truncate(inode, new_size); /* * If jinode is zero, then we never opened the file for @@ -135,10 +137,10 @@ static inline int ext4_begin_ordered_truncate(struct inode *inode, * jbd2_journal_begin_ordered_truncate() since there's no * outstanding writes we need to flush. */ - if (!EXT4_I(inode)->jinode) + if (!jinode) return 0; return jbd2_journal_begin_ordered_truncate(EXT4_JOURNAL(inode), - EXT4_I(inode)->jinode, + jinode, new_size); } @@ -4120,8 +4122,13 @@ int ext4_inode_attach_jinode(struct inode *inode) spin_unlock(&inode->i_lock); return -ENOMEM; } - ei->jinode = jinode; - jbd2_journal_init_jbd_inode(ei->jinode, inode); + jbd2_journal_init_jbd_inode(jinode, inode); + /* + * Publish ->jinode only after it is fully initialized so that + * readers never observe a partially initialized jbd2_inode. + */ + smp_wmb(); + WRITE_ONCE(ei->jinode, jinode); jinode = NULL; } spin_unlock(&inode->i_lock); -- 2.53.0